A £67m release clause in Haaland's contract will become active next year, and the Norway international is widely expected to move on, with Man United one of a number of clubs competing for his signature.
According to 90min, BVB are already preparing for the 21-year-old's departure and have identified Martial as a potential replacement for the centre-forward.
Martial has failed to score in six appearances for Ole Gunnar Solskjaer's side this season and failed to make the most of the opportunity to impress against West Ham United in the EFL Cup on Wednesday night.
The 25-year-old, who moved to Old Trafford from Monaco in September 2015, still has three years left to run on his contract with the 20-time English champions. body check tags ::